Printed circuit board

ABSTRACT

A printed circuit board includes: a core member including a through-hole; a sub-circuit board disposed in the through-hole; a first insulating layer disposed on opposing surfaces of the core member and opposing surfaces of the sub-circuit board; and an insulating material disposed between an inner wall of the through-hole and the sub-circuit board.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC 119(a) of Korean PatentApplication Nos. 10-2016-0048927 and 10-2016-0002884, filed on Apr. 21,2016 and Jan. 8, 2016, respectively, in the Korean Intellectual PropertyOffice, the entire disclosures of which are incorporated herein byreference for all purposes.

BACKGROUND

1. Field

The following description relates to a printed circuit board.

2. Description of Related Art

With the advancements in the computer industry, there have beenadvancements in the technology of manufacturing a die with higherperformance and a lower cost. Accordingly, various printed circuitboards have been developed to install the die therein.

Particularly, for substrates used in a server, it is difficult to have asufficient yield due to the multilayer structure and large size of thesubstrates. Additionally, a long lead time is required for theproduction of server substrates. Moreover, server substrates requiremultiple layers of via structure, precise construction and excellentelectrical properties.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In one general aspect, a printed circuit board includes: a core memberincluding a through-hole; a sub-circuit board disposed in thethrough-hole; a first insulating layer disposed on opposing surfaces ofthe core member and opposing surfaces of the sub-circuit board; and aninsulating material disposed between an inner wall of the through-holeand the sub-circuit board.

The printed circuit board may further include a via extending throughthe core member.

The sub-circuit board may include a circuit layer and a secondinsulating layer.

The insulating material may be made of a material different from amaterial of the second insulating layer.

The insulating material may be filled with a material of the firstinsulating layer.

The first insulating layer may further include fabric stiffener.

The sub-circuit board may include a coreless structure.

The sub-circuit board may include a reinforcing layer including fabricstiffener.

The sub-circuit board may include: a high density circuit; and a lowdensity circuit formed on one or both of the core member and the firstinsulating layer, and having a density lower than a density of the highdensity circuit.

The high density circuit may include stacked vias arranged symmetricallywith one another.

The printed circuit board may further include a via or a solder bumpconnecting the low density circuit with the high density circuit.

A distance between circuit layers of the high density circuit may beless than a distance between circuit layers of the low density circuit.

A width of the high density circuit may be less than a width of the lowdensity circuit.

The printed circuit board may further include an electronic deviceconnected to the high density circuit and encapsulated in the firstinsulating layer.

The printed circuit board may further include an outer layer circuitincluding a connection pad and a circuit pattern, wherein the connectionpad is formed on the first insulating layer and the circuit patternconnects the high density circuit to the connection pad.

The low density circuit layer may include low density circuit layersdisposed on the core member and the sub-circuit board.

The first insulating layer may be laminated on the opposing surfaces ofthe core member and the opposing surfaces of the sub-circuit board.

In another general aspect, a printed circuit board includes: a firstcircuit board including a first circuit; and a second circuit boardembedded in the first circuit board between insulators, wherein thesecond circuit board includes a second circuit connected to the firstcircuit, and wherein the second circuit includes a circuit patterndensity that is higher than a circuit pattern density of the firstcircuit.

The insulators may include: a laminated insulating layer disposed onopposing surfaces of the core member and opposing surfaces of thesub-circuit board; and an insulating material disposed between the firstcircuit board and the second circuit board.

The second circuit may include a circuit layer disposed in a corelessinsulating material.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example of a printed circuit board connected to adie.

FIG. 2 illustrates a via structure in a high density circuit of anexample of a printed circuit board.

FIG. 3 to FIG. 14 illustrate an example of a method of manufacturing aprinted circuit board.

FIG. 15 illustrates another example of a printed circuit board connectedto a die.

FIG. 16 illustrates yet another example of a printed circuit board.

FIG. 17 to FIG. 25 illustrate another example of a method ofmanufacturing a printed circuit board.

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements. The drawings may not be to scale,and the relative size, proportions, and depiction of elements in thedrawings may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent after an understanding of thedisclosure of this application. For example, the sequences of operationsdescribed herein are merely examples, and are not limited to those setforth herein, but may be changed as will be apparent after anunderstanding of the disclosure of this application, with the exceptionof operations necessarily occurring in a certain order. Also,descriptions of features that are known in the art may be omitted forincreased clarity and conciseness.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided merelyto illustrate some of the many possible ways of implementing themethods, apparatuses, and/or systems described herein that will beapparent after an understanding of the disclosure of this application.

As used herein, the term “and/or” includes any one and any combinationof any two or more of the associated listed items.

Although terms such as “first,” “second,” and “third” may be used hereinto describe various members, components, regions, layers, or sections,these members, components, regions, layers, or sections are not to belimited by these terms. Rather, these terms are only used to distinguishone member, component, region, layer, or section from another member,component, region, layer, or section. Thus, a first member, component,region, layer, or section referred to in examples described herein mayalso be referred to as a second member, component, region, layer, orsection without departing from the teachings of the examples.

Spatially relative terms such as “above,” “upper,” “below,” and “lower”may be used herein for ease of description to describe one element'srelationship to another element as shown in the figures. Such spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. For example, if the device in the figures is turned over,an element described as being “above” or “upper” relative to anotherelement will then be “below” or “lower” relative to the other element.Thus, the term “above” encompasses both the above and below orientationsdepending on the spatial orientation of the device. The device may alsobe oriented in other ways (for example, rotated 90 degrees or at otherorientations), and the spatially relative terms used herein are to beinterpreted accordingly.

The terminology used herein is for describing various examples only, andis not to be used to limit the disclosure. The articles “a,” “an,” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. The terms “comprises,” “includes,”and “has” specify the presence of stated features, numbers, operations,members, elements, and/or combinations thereof, but do not preclude thepresence or addition of one or more other features, numbers, operations,members, elements, and/or combinations thereof.

Due to manufacturing techniques and/or tolerances, variations of theshapes shown in the drawings may occur. Thus, the examples describedherein are not limited to the specific shapes shown in the drawings, butinclude changes in shape that occur during manufacturing.

The features of the examples described herein may be combined in variousways as will be apparent after an understanding of the disclosure ofthis application. Further, although the examples described herein have avariety of configurations, other configurations are possible as will beapparent after an understanding of the disclosure of this application.

FIG. 1 illustrates an example of a printed circuit board 10. Referringto FIG. 1, the printed circuit board 10 includes a sub-circuit board100, a core member 155, a first insulating layer 180 and an insulatingmaterial 185.

The sub-circuit board 100 is another circuit board encapsulated in theprinted circuit board 10 and includes at least one circuit layer and asecond insulating layer 105 configured to insulate the at least onecircuit layer from other layers and/or components. The at least onecircuit layer is, for example, embedded in second insulating layer 105.The sub-circuit board 100 may perform a particular function that is notprocessed by any other region of the printed circuit board 10. Forexample, the sub-circuit board 100 is electrically connected to a die 1installed on the printed circuit board 10 to perform, for example, atransfer of an electric signal. In the example described herein, the die1 is an integrated circuit. The sub-circuit board 100 includes a highdensity circuit 110 including a fine circuit pattern 120. The highdensity circuit 110 is highly concentrated in a small space in order tobe connected to the die 1.

In the sub-circuit board 100, a width and an inter-circuit distance ofthe high density circuit 110 may be less than a width and aninter-circuit distance, respectively, of a low density circuit 160,which will be described later. Moreover, the high density circuit 110may be formed to be finer than an outer circuit layer 165, which isformed on an outer layer of the sub-circuit board 100 after thesub-circuit board 100 is encapsulated. For example, the high densitycircuit 110 is formed using, a semiconductor process, and the lowdensity circuit 160 is formed through a semi-additive process (SAP), amodified semi-additive process (M-SAP) or a tenting process.Alternatively, the high density circuit 110 may be formed using the SAP,which is a relatively more precise substrate process, and the lowdensity circuit 160 may be formed using the M-SAP or the tentingprocess, which is a relatively less precise substrate process.

The sub-circuit board 100 may be formed in a coreless structure, thatis, a structure having no reinforcing member in the middle of thesub-circuit board 100. For example, the sub-circuit board 100 is formedby successively laminating layers of the fine circuit pattern 120 andthe second insulating layer 105 for insulating the fine circuit pattern120, without any reinforcing member in the middle of the layers of thefine circuit pattern 120 and the second insulating layer 105. In orderto prevent the coreless structure of sub-circuit board 100 from warpingdue to physical forces or environmental temperature changes, forexample, a reinforcing layer having fabric stiffener included in thereinforcing layer may be added to the sub-circuit board 100. Forexample, a prepreg layer is additionally laminated on a circuit layerthat is built up with the fine circuit pattern 120 and the secondinsulating layer.

The sub-circuit board 100 includes a pad 130 formed on one surface ofthe sub-circuit board 100. Although not shown in the example of FIG. 1,the die 1 may be directly coupled to the pad 130, such that thesub-circuit board 100 may be directly connected with the die 1. The onesurface of the sub-circuit board 100 on which the pad 130 is formed maybe an outer layer of the printed circuit board 10.

Alternatively, as illustrated in FIG. 1, the sub-circuit board 100 mayinclude an outer layer formed on the one surface of the sub-circuitboard 100 on which the pad 130 is formed, and the outer circuit layer165 for connecting the die 1 with the high density circuit 110 may beformed on the outer layer of the sub-circuit board 100. As illustratedin FIG. 1, the outer circuit layer 165 includes a pad for connectionwith the die 1 and is connected with the pad 130 of the high densitycircuit 110. The outer circuit layer 165 may be directly soldered on thehigh density circuit 110 to prevent damage to the high density circuit110.

In an example, the outer circuit layer 165 includes a fan-out circuitpattern for fanning out the high density circuit 110. That is, thecircuit pattern of the high density circuit 110 of the sub-circuit board100 may be spread out and dispersed by being connected to the lowerdensity fan-out circuit pattern of the outer circuit layer 165. Thefan-out circuit pattern may include a pad formed on the outer layer ofthe printed circuit board in accordance with the dimensions of the die1. Accordingly, the high density circuit 110 may be designed free of thedimensions of the die 1, thereby providing a higher freedom of design ofthe high density circuit 110.

FIG. 2 illustrates a via structure in the high density circuit 110.Referring to FIG. 2, the high density circuit 110 includes stacked vias125 a, 125 b, which are laminated or disposed to be symmetrical to eachother. In order to minimize warpage of the sub-circuit board 100, thevias 125 a, 125 b may be laminated symmetrically about a center portionof the sub-circuit board 100. A few via layers may be initiallylaminated on one side only, and then remaining via layers may besuccessively laminated on either side to form the symmetrical structureof stacked vias 125 a, 125 b. In an example in which the vias 125 a, 125b are laminated in the high density circuit 110, the vias 125 a, 125 bare included in a structure formed of layers of doth or paper with athermoset resin that are cured under pressure and temperature.

Referring to FIG. 1, the core member 155 forms a center portion of theprinted circuit board 10, and works with a first insulating layer 180disposed on opposite surfaces (for example, upper and lower surfaces) ofthe core member 155 to resist or prevent warpage of the sub-circuitboard 100. For example, to provide warpage resistance, the core member155 is made of a material having a higher rigidity than a rigidity ofthe sub-circuit board 100 and the first insulating layer 180, and athrough-hole C (FIG. 6) is formed in the core member 155 to accommodatethe sub-circuit board 100 in the through-hole C.

For example, the core member 155 is an insulating substrate having areinforcing material, such as glass fiber or carbon fiber, impregnatedin an insulating resin or is a metal core made of a metallic material.However, the core member 155 may be made of a variety of othermaterials. Moreover, the core member 155 is penetrated by a via 156. Thevia 156 provides an electrical connection to the upper and lowersurfaces of the core member 155. Referring to FIG. 1, the low densitycircuits 160 formed on the upper surface and the lower surface of thecore member 155 are connected to each other through the via 156.

By having the sub-circuit board 100 encapsulated in the core member 155,a region in which the sub-circuit board 100 is encapsulated may not needto have a thick core structure. Accordingly, the via 156 is not disposedin the region of the core member 155 in which the sub-circuit board 100is encapsulated. Due to the processing restrictions, the via 156 cannotbe formed in a small distance. Therefore, by omitting a via, such as thevia 156, which penetrates entirely through the core member 155 in theregion of the core member 155 in which the sub-circuit board 100 isencapsulated, and substituting such via penetrating the core member 155with the stacked vias 125 a, 125 b of the sub-circuit board 100, it ispossible to have a fine pitch between the vias 125 a, 125 b. Moreover,by having the core structure omitted at the through-hole C, it ispossible to reduce double layers on an upper surface and a lower surfaceof the core member 155. By reducing the distance between the vias andthe circuit layer on upper and lower surfaces of the core, it ispossible to reduce the routing distance of the circuit and decrease thenumber of layers and the size of the overall substrate. Moreover, byreplacing the via 156 of the core member 155 and the vias connectedthereto with the stacked vias in the region in which the sub-circuitboard 100 is encapsulated, it is possible to prevent a stress issuecaused by a difference in the coefficient of thermal expansion betweenthe via 156 of the core member 155 and the vias connected thereto.

The first insulating layer 180 is laminated on both (e.g., upper andlower) surfaces of the core member 155 and the sub-circuit board 100 tocouple both surfaces of the sub-circuit board 100, which is disposed inthe through-hole C, with the core member 155.

Referring to FIG. 1, the core member 155 is used as a middle layer ofthe printed circuit board, and the sub-circuit board 100 is disposed inthe through-hole C. The core member 155 and the sub-circuit board 100are coupled with each other by the first insulating layer 180. Forinstance, the core member 155 has the shape of a rectangular frame, andthe sub-circuit board 100 is structured to be disposed and encapsulatedwithin the rectangular frame. Due to the first insulating layer 180being laminated on both surfaces of the core member 155 and thesub-circuit 100, the core member 155 secures the sub-circuit board 100to prevent the warpage of the sub-circuit board 100.

The first insulating layer 180 may contain fabric stiffener, such asglass fiber. For instance, the first insulating layer 180 is formed froma laminated prepreg. The first insulating layer 180 containing thefabric stiffener further reinforces the rigidity of the sub-circuitboard 100 when the sub-circuit board 100 and the core member 155 areintegrally structured.

Referring to FIGS. 1 and 6, insulating material 185 is disposed betweenan inner wall 155 a of the through-hole C and the sub-circuit board 100to couple a side wall of sub-circuit board 100 with the core member 155.More specifically, when the sub-circuit board 100 is initially disposedin the through-hole C of the core member 155, a gap is formed betweenthe inner wall 155 a of the through-hole C and the sub-circuit board100. The insulating material 185 fills the gap and, at the same time,couples the core member 155 with the sub-circuit board 100. Accordingly,by allowing the core member 155 to fasten the sub-circuit board 100, theinsulating material 185 prevents warpage of the sub-circuit board 100.

The insulating material 185 may be made of a different material fromthat of the second insulating layer 105 of the sub-circuit board 100.For example, the insulating material 185 is formed by having some of theinsulating material of the first insulating layer 180 filled therein. Ina case where the first insulating layer 180 contains fabric stiffener,the insulating material 185 may also contain the fabric stiffener.Moreover, the insulating material 185 may be formed by filling aseparate material in between the inner wall 155 a of the through-holeand the sub-circuit board 100 before the first insulating layer 180 islaminated.

In a printed circuit board, areas excluding areas where a high densitycircuit is needed for special purposes or applications may not need toinclude a high density circuit. Therefore, in an embodiment, a lowdensity circuit, which has a higher yield and is less expensive, may bedisposed in areas where a high density circuit is not needed.Accordingly, the low density circuit 160, which has a lower circuitpattern density than a circuit pattern density of the high densitycircuit 110, is formed in a region including the core member 155 and thefirst insulating layer 180.

For example, the low density circuit 160 is formed at an inside oroutside of one or both of the core member 155 and the first insulatinglayer 180. In the embodiment illustrated in FIG. 1, the low densitycircuit is formed between the core member 155 and the first insulatinglayer 180 on the upper and lower surfaces of the core member 155.Accordingly, the core member 155, the first insulating layer 180 and thelow density circuit 160 integrally form a low density printed circuitarea, and the printed circuit board 10 has an overall structure in whichthe sub-circuit board 100 containing the high density circuit 110 isencapsulated in the low density printed circuit area.

Since the sub-circuit board 100 has circuit layers having a highercircuit pattern density than a circuit pattern density of the lowdensity printed circuit area, a distance between the circuit layers inthe sub-circuit board 100 is less than a distance between the circuitlayers in the low density printed circuit area. For instance, multiplecircuit layers of the sub-circuit board 100 are encapsulated in a singleinsulating layer of the low density printed circuit area. Theencapsulated sub-circuit board 100 may be covered by an outer layer ofthe low density printed circuit area.

Moreover, the low density printed circuit area may be formed to conformto a form factor of a server substrate. The form factor refers to thesize, configuration and physical arrangement of a circuit board, such asa server substrate, having a specific purpose, and is a standard forconfiguring the hardware. In the printed circuit board 10, the lowdensity printed circuit area may be formed to correspond to the formfactor, and the sub-circuit board 100 may be freely formed. For example,the low density circuit board area, which corresponds to the formfactor, has a layout based on the standard, and the sub-circuit board100, which is an area outside the form factor, can be fabricated invarious sizes and forms.

The low density circuit board area is provided with a space for mountinga part on the die side. For example, a first electronic device 140, suchas a die side capacitor, is mounted on an outer layer 187 of the serversubstrate/printed circuit board 10 in the low density circuit boardarea. More specifically, the first electronic device 140 is connected toa circuit pattern 162 of the low density circuit 160. The outer layer187 is, for example, a solder resist layer disposed on outer surfaces ofthe first insulating layer 180 at upper and lower sides of the serversubstrate/printed circuit board 10. The low density circuit board areamay have a ground GND formed therein, and the ground may be connected tothe sub-circuit board 100 through a via.

Referring to FIG. 1, the low density circuit board area further includesa via 170 or a solder bump connecting the low density circuit 160 withthe high density circuit 110 of the sub-circuit board 100. In theexample shown, the via 170 connects a layer of the low density circuit160 on the lower side of the printed circuit board 10 with a layer ofthe high density circuit 110 on the lower side of the printed circuitboard 10. The low density circuit 160 includes a pad 161 that isdisposed on the lower side of the sub-circuit board 100 and a circuitpattern 162 connected to the pad. Referring to FIG. 1, the low densitycircuit 160 and the high density circuit 110 are directly connected toeach other vertically through the via 170, which is connected to thecircuit pattern 162. Accordingly, the routing distance of asignal-transferring circuit may be reduced to enhance the electricalreliability of the printed circuit board 10.

FIGS. 3 to 14 illustrate processes of an example of a method ofmanufacturing the printed circuit board 10. The method generallyincludes coupling and encapsulating the sub-circuit board 110 in a lowdensity printed circuit board having the core member 155 providedtherein.

Referring to FIG. 3 to FIG. 5, the core member 155 having a metal layer160 a formed on upper and lower surfaces thereof is provided, and aportion of the low density circuit 160 including the via 156 penetratingthe core member 155 is formed by removing portions of the metal layer160 a to form the pad 161, and removing additional portions of the metallayer 160 a and portions of the core member 155 to form a via hole 156 aand filling the via hole 156 a with a conductive material. Referring toFIG. 6, a through-hole C is formed by removing corresponding portions ofthe metal layer 160 a and the core member 155.

Referring to FIG. 7, the sub-circuit board 100 having a high densitycircuit 110 provided therein is prepared, and the sub-circuit board 100is positioned inside the through-hole C. An adhesive tape 155 b isattached on one surface of the core member 155 to secure the sub-circuitboard 100 in the through-hole C.

Referring to FIG. 8, the first insulating layer 180 is laminated onanother surface of the core member 155 opposite the one surface on whichthe adhesive tape is attached, and the sub-circuit board 100 isencapsulated by filling the insulating material 185 in the gap betweenthe inner wall 155 a of the through-hole C and the sub-circuit board100. The insulating material 185 may be formed by having some of aninsulating material of the first insulating layer 180 filled in the gapbetween the inner wall 155 a of the through-hole C and the sub-circuitboard 100. The first insulating layer 180 may contain fabric stiffener,such as glass fiber.

Referring to FIG. 9, the adhesive tape 155 b is removed from the onesurface of the core member 155, and the first insulating layer 180 islaminated on the one surface of the core member 155. As a result, bothsurfaces of the sub-circuit board 100 are tightly coupled with the coremember 155 to prevent warpage.

Referring to FIG. 10 and FIG. 11, the outer layer circuit 165 is formedto be connected with one surface of the sub-circuit board 100. The via170 and the circuit pattern 162 of the low density circuit 160 connectedwith the via 170 is formed on the other surface of the sub-circuit board100. Referring to FIG. 12, a solder resist layer 187 is formed as anouter layer of the printed circuit board 10, on the first insulatinglayer 180 on the one surface and the other surface of the core member155.

Referring to FIG. 13, the solder bump 175 is formed on the outer layercircuit 165 exposed to one surface of the printed circuit board 10through an opening of the solder resist layer 187, and the firstelectronic device 140 is installed on the other surface of the printedcircuit board 10. Referring to FIG. 14, the die 1 is installed on theone surface of the printed circuit board 10 and connected to the outerlayer circuit 165 through the solder bump 175. Additional firstelectronic devices 140 are installed on the one surface of the printedcircuit board 10.

FIG. 15 illustrates yet another example of a printed circuit board 10 a.The printed circuit board 10 a is similar to the printed circuit board10 of FIG. 1, except that the printed circuit board 10 a includes asub-circuit board 100 a. The sub-circuit board 100 a is similar to thesub-circuit board 100, except that the sub-circuit board 10 a includes asecond electronic device 190 that is connected to the high densitycircuit 110 and encapsulated in the first insulating layer 180. Forexample, the sub-circuit board 100 a includes the second electronicdevice 190, which may be an active device or a passive device such as acapacitor, mounted on the outer layer of the sub-circuit board 100 a.The second electronic device 190 is mounted, for example, on an uppersurface of the sub-circuit board 100 a. Particularly, the secondelectronic device 140 may be a die side capacitor, which has beenconventionally mounted on an outer layer of a printed circuit board, andmay be mounted on the sub-circuit board 100 a and then encapsulated inthe printed circuit board 10 a. Moreover, in order to support thefunction of the die 1, the second electronic device 190 is configured toroute and transfer power of a micro electronic device/system.

FIG. 16 illustrates yet another example of a printed circuit board 10 b.Referring to FIG. 16, the printed circuit board 10 b is similar to theprinted circuit board 10 of FIG. 1, but further includes multiple lowdensity circuit layers 200 a laminated on the other surface (forexample, the lower surface) of the sub-circuit board 100. In otherwords, the printed circuit board 10 b includes the printed circuit board10 in accordance with the example of FIG. 1, without the circuit pattern162 on the lower side thereof, as an upper substrate and the multiplelow density circuit layers 200 a as a lower substrate.

The multiple low density circuit layers 200 a are connected so as tosupport the upper substrate having the sub-circuit board 100encapsulated therein. A circuit 210 of the multiple low density circuitlayers 200 a is connected with the sub-circuit board 100 and the lowdensity circuit 160 of the upper substrate through a via 220. As themultiple low density circuit layers 200 a have thicker circuit andinsulating layer than those of the sub-circuit board 100, the lowdensity circuit layers 200 a may have a higher rigidity than the uppersubstrate having the sub-circuit board 100 encapsulated therein.Accordingly, the multiple low density circuit layers 200 a may functionto prevent the warpage of the sub-circuit board 100 and the uppersubstrate.

FIGS. 17 to 26 are processes of an example of a method of manufacturingthe printed circuit board 10 b. The method generally includes couplingand encapsulating the sub-circuit board 100 in the core member 155 andthe low density circuit board including the multiple low density circuitlayers 200 a provided therein.

Referring to FIG. 17 and FIG. 18, a carrier 5 is prepared, and adhesivelayers 6 are formed on opposite surfaces (such as upper and lowersurfaces) of the carrier 5. Referring to FIG. 19, the core members 155,each having a through hole C, a portion of the low density circuit 160and a via 156 formed therein, are attached to the opposite surfaces ofthe carrier 5 using the adhesive layers 6. In the following paragraphs,further operations will be described with respect to a single coremember 155 attached to one surface of the carrier 5 and having thethrough hole C, the portion of the low density circuit 160 and the via156 formed therein. However, it should be understood that the followingoperations are repeated for the additional core member 155 attached tothe opposite surface of the carrier 5 and having the through hole C, theportion of the low density circuit 160 and the via 156 formed therein.

Referring to FIG. 20, the sub-circuit board 100 having the high densitycircuit 110 provided therein is prepared, and the sub-circuit board 100is positioned inside the through-hole C. The sub-circuit board 100 isdisposed in such a way that the sub-circuit board 100 is inverted. Inother words, one surface of the sub-circuit board 100 to which the die 1is to be connected is oriented toward the carrier 5.

Referring to FIG. 21, the first insulating layer 180 is laminated orotherwise applied on the other surface of the core member 155, and thesub-circuit board 100 is encapsulated by filling an insulating material185 in the gap between the sub-circuit board 100 and the core board 155(that is, the gap between the inner wall 155 a of the through-hole C andthe sub-circuit board 100). The first insulating layer 180 containingfabric stiffener is laminated on the sub-circuit board 100 and the coremember 155 to couple the sub-circuit board 100 to the core member 155more tightly.

Referring to FIG. 22, the multiple low density circuit layers 200 a areformed on two upper substrates formed on either surface of the carrier5. For example, the via 220 connected with the low density circuitlayers 200 a and the high density circuit 110 is formed on the othersurface of the sub-circuit board 100. The insulating layer 180 includinga fabric stiffener is applied to the multiple low density circuit layers200 a, between the low density circuit layers 200 a and the core member155, in order to prevent warpage.

Referring to FIG. 23 and FIG. 24, the outer layer circuit 165 connectedwith one surface of the sub-circuit board 100 is formed after separatingthe carrier 5 from the core member 155. A solder resist layer 187 isformed on an outer layer of the printed circuit board 10 b.

Referring to FIG. 25, the die 1 is installed using the solder bump 175on the outer layer circuit 165 exposed at one surface of the printedcircuit board 10 b through an opening of the solder resist layer 187,and the first electronic device 140 may be installed on the othersurface of the printed circuit board.

While this disclosure includes specific examples, it will be apparentafter an understanding of the disclosure of this application thatvarious changes in form and details may be made in these exampleswithout departing from the spirit and scope of the claims and theirequivalents. The examples described herein are to be considered in adescriptive sense only, and not for purposes of limitation. Descriptionsof features or aspects in each example are to be considered as beingapplicable to similar features or aspects in other examples. Suitableresults may be achieved if the described techniques are performed in adifferent order, and/or if components in a described system,architecture, device, or circuit are combined in a different manner,and/or replaced or supplemented by other components or theirequivalents. Therefore, the scope of the disclosure is defined not bythe detailed description, but by the claims and their equivalents, andall variations within the scope of the claims and their equivalents areto be construed as being included in the disclosure.

What is claimed is:
 1. A printed circuit board, comprising: a coremember comprising a through-hole; a sub-circuit board disposed in thethrough-hole; a first insulating layer disposed on opposing surfaces ofthe core member and opposing surfaces of the sub-circuit board; and aninsulating material disposed between an inner wall of the through-holeand the sub-circuit board.
 2. The printed circuit board of claim 1,further comprising a via extending through the core member.
 3. Theprinted circuit board of claim 1, wherein the sub-circuit boardcomprises a circuit layer and a second insulating layer.
 4. The printedcircuit board of claim 3, wherein the insulating material is made of amaterial different from a material of the second insulating layer. 5.The printed circuit board of claim 4, wherein the insulating material isfilled with a material of the first insulating layer.
 6. The printedcircuit board of claim 1, wherein the first insulating layer furthercomprises fabric stiffener.
 7. The printed circuit board of claim 1,wherein the sub-circuit board comprises a coreless structure.
 8. Theprinted circuit board of claim 1, wherein the sub-circuit boardcomprises a reinforcing layer comprising fabric stiffener.
 9. Theprinted circuit board of claim 1, wherein the sub-circuit boardcomprises: a high density circuit; and a low density circuit formed onone or both of the core member and the first insulating layer, andcomprising a density lower than a density of the high density circuit.10. The printed circuit board of claim 9, wherein the high densitycircuit comprises stacked vias arranged symmetrically with one another.11. The printed circuit board of claim 9, further comprising a via or asolder bump connecting the low density circuit with the high densitycircuit.
 12. The printed circuit board of claim 9, wherein a distancebetween circuit layers of the high density circuit is less than adistance between circuit layers of the low density circuit.
 13. Theprinted circuit board of claim 9, wherein a width of the high densitycircuit is less than a width of the low density circuit.
 14. The printedcircuit board of claim 9, further comprising an electronic deviceconnected to the high density circuit and encapsulated in the firstinsulating layer.
 15. The printed circuit board of claim 9, furthercomprising an outer layer circuit comprising a connection pad and acircuit pattern, wherein the connection pad is formed on the firstinsulating layer and the circuit pattern connects the high densitycircuit to the connection pad.
 16. The printed circuit board of claim 9,wherein the low density circuit layer comprises low density circuitlayers disposed on the core member and the sub-circuit board.
 17. Theprinted circuit board of claim 1, wherein the first insulating layer islaminated on the opposing surfaces of the core member and the opposingsurfaces of the sub-circuit board.
 18. A printed circuit board,comprising: a first circuit board comprising a first circuit; and asecond circuit board embedded in the first circuit board betweeninsulators, wherein the second circuit board comprises a second circuitconnected to the first circuit, and wherein the second circuit comprisesa circuit pattern density that is higher than a circuit pattern densityof the first circuit.
 19. The printed circuit board of claim 18, whereinthe insulators comprise: a laminated insulating layer disposed onopposing surfaces of the core member and opposing surfaces of thesub-circuit board; and an insulating material disposed between the firstcircuit board and the second circuit board.
 20. The printed circuitboard of claim 18, wherein the second circuit comprises a circuit layerdisposed in a coreless insulating material.